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Abstract:
We present a search for gravitational waves from 222 pulsars with rotation
frequencies $\gtrsim 10$ Hz. We use advanced LIGO data from its first and
second observing runs spanning 2015-2017, which provides the highest
sensitivity gravitational-wave data so far obtained. In this search we target
emission from both the $l = m = 2$ mass quadrupole mode, with a frequency at
twice that of the pulsar's rotation, and from the $l = 2$, $m = 1$ mode, with a
frequency at the pulsar rotation frequency. The search finds no evidence for
gravitational-wave emission from any pulsar at either frequency. For the $l = m
= 2$ mode search, we provide updated upper limits on the gravitational-wave
amplitude, mass quadrupole moment, and fiducial ellipticity for 167 pulsars,
and the first such limits for a further 55. For 20 young pulsars these results
give limits that surpass those inferred from the pulsars' spin-down. For the
Crab and Vela pulsars our results constrain gravitational-wave emission to
account for less than 0.017% and 0.18% of the spin-down luminosity,
respectively. For the recycled millisecond pulsar J0711-6830 our limits are
only a factor of 1.3 above the spin-down limit, assuming the canonical value of
$10^{38}$ kg m$^2$ for the star's moment of inertia, and imply a
gravitational-wave derived upper limit on the star's ellipticity of
$1.2\!\times\!10^{-8}$. We also place new limits on the emission amplitude at
the rotation frequency of the pulsars.